A prior art frictionless solenoid operable in association with a liquid controlling valve is illustrated in FIG. 1. The illustration in FIG. 1 represents the closest prior art known to the inventor.
The solenoid portion 10 of the solenoid operated valve 11 consists of an armature 12 suspended in the center of an annular coil 13 by a pair of flat substantially linear springs 14 and 16 attached to the armature 12 at one end and attached to the solenoid pole pieces 17 and 18 at the other end to prevent radial movements. The pole pieces 17 and 18 are oriented at the ends of the annular coil 13 and are connected together by a metal tube 19 made of a magnetic material which is oriented around the outside of the annular coil 13. The tube serves the purpose of completing the flux carrying magnetic circuit.
The pole piece 17 oriented to the left of the annular coil has a large opening 21 in it and is adapted to receive therein the armature 12. The radial space between the outside diameter of the armature 12 and the inside diameter of the opening 21 serves to define a non-working air gap 22. This end of the armature also has an elongate rod 23 formed on the left axial end face of the armature and it is this rod 23 that is secured to the aforesaid spring 14. A hole in the center of the spring 14 allows the rod 23 to extend therethrough. A resilient spacer 24 is provided to space the spring 14 from the axial end face of the armature 12 and a retainer ring 26 is utilized to hold the spring 14 against the resilient spacer 24.
The opposite pole piece 18 also has a hole 27 extending therethrough. The armature has a non-magnetic rod 28 formed on the right axial end face of the armature and extends axially away therefrom into and through a hole in the spring 16 whereat it is fixedly attached to the rod 28. The two springs 14 and 16 serve to suspend the armature 12 and the two axially protruding rods 23 and 28 in the respective holes through the pole pieces 17 and 18 as well as through the central hole in the annular coil 13 so as to create a frictionless support for the armature.
In this particular prior art construction, a liquid control valve is oriented at the right end of the housing 29 which houses the aforesaid armature 12 and annular coil 13. The liquid control valve 31 includes a central bore 32 therethrough having a plurality of liquid ports therein, namely, a liquid supply port 33, a control port 34 and a tank port 36. A nozzle 37 is provided in the bore 32 between the supply port 33 and the tank port 36 axially spaced from the supply port 33. The nozzle 37 has a nozzle opening 38 therein so that liquid supplied through the supply port 33 to the control port 34 is bled through the nozzle opening 38 to the tank port 36 when a button 39 fixedly secured to the rod 28 and movable therewith is spaced away from the nozzle opening 38 as illustrated in FIG. 1.
The right axial end face of the armature 12 is normally axially spaced from the left axially facing surface of the pole piece 18 when the annular coil 13 is not electrically energized. The axial space defines a working air gap 41. As a result, when the annular coil 13 is electrically energized, the armature 12 will be driven rightwardly toward the pole piece 18. In addition, the right axial end face 42 will move into close relation with the nozzle opening 38 to block liquid flow from the control port 34 to the tank port 36. As a result, pressure will build up in the control port 34 to effect an appropriate drive of a mechanism connected thereto.
Electrical energy is supplied to the annular coil 13 through a electrical connection 43.
Due to the precise control and response required from this type of solenoid operated liquid valve, and recognizing that these solenoid operated valves are sensitive to variations and changing conditions within the total liquid (here hydraulic) system, these variations can lead to an undesirable natural frequency oscillation in the armature 12. Such items that influence the sensitivity are fluid viscosity changes due to temperature change, changes in the resilience of rubber components and also any spring loading that may be provided in valve arrangements which include spring loaded control spools. Variations caused by these system components are unacceptable. The invention set forth herein successfully resolves the issue of natural frequency system oscillations.